The invention relates to the bracing of deformable vehicle body structures of a resiliently front mounted engine of a motor vehicle, wherein after a partial deformation of the car front in the case of a frontal collision, a longitudinally extending tension band, fastened to the vehicle body structure laterally adjacent to the engine, is braced frictionally on the engine side of the vehicle.
Bracing of the engine of a motor vehicle is known from DE-OS 2,506,303. In this case, the bracing is formed by a transverse beam strip iron which extends from the front portion of the engine gear box unit and is attached rigidly to longitudinal side members of the associated motor car, laterally adjacent to the engine on both sides.
In the cae of a frontal collision with an obstacle, this transverse beam arrangement results in both longitudinal side members being utilized as crush zones, largely independently of the degree of the length of the beam, and in the case of major deformations of the car front, the engine unit is displaced toward the rear along with the side members until the rear end face of the engine block is braced against the end wall of the vehicle body located at the passenger compartment safety cell, and involves the latter in the absorption of impact energy. These deformations in the central region of the end wall have a disadvantageous effect upon the so-called survival space in the interior of the safety cell in the case of substantial deformations of the safety cell.
However, in the case of a non head-on collision, which occurs frequently, the above design prevents deformation energy from being absorbed by that half of the car front structure on the non-collision side.
In this case, collapsing of the end wall into the foot space of the safety cell on the collision side would endanger the preservation of the necessary passenger survival space and would be expected even in the case of relatively low collision velocities. Because adequate installation space for a crossbar-like collision absorption mechanism will frequently not be present in the engine compartment of motor cars in front of the engine, DE-OS No. 2,506,303 provides as an alternative to the known bracing, a plurality bracing for the engine laterally.
A lateral engagement of a support band, to fasten to longitudinal members with a loop-shaped strip iron which comes into abutment with a projection protruding laterally from the engine in the course of the deformation of the car front was provided.
Although the resiliently mounted engine then remains freely movable relative to the vehicle body surrounding it, such an arrangement can only be designed for a precisely defined course of deformation of the car front.
However, since the course of deformation of the car front varies considerably according to the direction of impact with the obstacle, a reliable bracing function on the engine is not immediately ensured.
For the reasons explained supra, it is an underlying object of this invention to provide a bracing of the vehicle body structure, deformed with absorption of energy on a resiliently mounted front engine of motor vehicles, so that the braking function of the front engine can occur largely independently of the direction of deformation of the car front in the case of a frontal collision, and with the object of using a tension band arrangement that requires little installation space.
According to the invention, the tension band is constructed as a flexible tension cable at least along a part of its length and is connected permanently to the engine and the vehicle body at its ends by fasteners. The tension band is retained between its fasteners so that it is tensioned with absorption of the forces after the conclusion of the intended partial deformation of the vehicle body structure associated with it.
The normal resilient mounting of the engine to allow for vibration is not prejudiced by this mounting arrangement, although a permanent connection exists between the engine and the vehicle body.
The flexible bracing also prevents a noticeable increase in the transmission of sound which would occur through a solid connection from the engine to the vehicle body.
It also has the advantage that the tension band need be oriented only in the longitudinal direction of the vehicle while connected between the engine and side wall of the engine compartment, appropriate to the installation space available. The collision force-absorbing tensioned position of the tension band occurs only after a longitudinal deformation of the side wall of the vehicle body by more than 30 mm.
Different mountings of the tension band are advantageous according to the location of the engine in the motor car. In the case of an engine installed offset to the right in the engine compartment, it may be sufficient if the tension band is arranged on the left-hand side between a longitudinal side member and the opposite side of the engine from the longitudinal side members, because there is a high probability that the engine will be involved in stress on its end face in the case of a right-hand offset collision of the motor car.
It is also possible to select the fastening points so that the engine unit is pivoted somewhat about an almost vertical axis under tensile loading by the tension band. In the case of an offset crash, this produces an oblique displacement of the engine unit out of its position parallel with respect to the median longitudinal axis towards the tension band side, which gives the engine unit a direction towards the side of the motor car remote from the crash.
Although a drive side offset collision is substantially more frequent than one on the passenger side, a tension band may be provided on each of the two sides of the engine, particularly in the case of a centrally arranged engine unit. In this case, a tension band arrangement oriented in mirror image to the median longitudinal axis of the motor vehicle is selected, with the required bracing behavior of the engine being obtained irrespective of the offset collision side of the motor vehicle.
The tension band arrangement can also be used simultaneously as an electrical grounding cable from the engine to the vehicle body. This attribution of a dual function to the tension band achieves an economy in weight compared to fitting the tension band in addition to a grounding cable.
If the tension band is required to be attached on the engine side to components which are made of cast materials, then the self-damping which exists per se in the case of wire cables as a tension band is no longer sufficient to prevent the cable from being torn out of the casting in the course of the abrupt transmission of tensile forces which occurs in the course of the tensioning process of the tension band. Thus, it is necessary in this case for a part of the existing tensioning length to be formed by a deformation element, which deforms plastically in the final phase of the tensioning process of the tension band, so that the tensile stress can be transmitted to the cast material more uniformly and without an extreme tension peak. With appropriate dimensioning of the deformation element, it is possible to prevent the engine side tension band fastening means from being torn apart.
A number of types of construction for such a deformation element may be used. The deformation element may comprise having a central region of the flexible tension band wound in meander shape around two transverse bolts of a cable joint in loops, which are pressed together by means of the cable joint, so that the tension band is elongated into its stretched tensioning position only by plastic bending open of the cable joint.
Alternatively, an end of the tension band could be formed as a cylinder arranged on the vehicle body with a displacer piston located therein and which is connected to the tension band in the manner of a piston rod, and wherein the displacer piston can be drawn into its limit position in the cylinder counter to plastic material deformation caused by a plastic material in the cylinder.
Another alternative would be to have two juxtaposed flat irons provided as tension band receivers and which are mutually flexurally rigidly connected toward the front end of the vehicle and wherein one of the flat irons is fastened at its rear end to the vehicle body and the other flat iron is fastened at its rear end to the engine by means of the tension band so that the pair of flat irons are spreadable in their flexurally rigid connection region with a plastic deformation.
However, combinations of tension cables with other deformation elements of comparable absorptive capacity are also conceivable.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.